When an optical lens is attached to a lens barrel by means of press-fitting, ribs (projections) are formed on an inner periphery of the lens barrel (a lens-retaining surface) or an outer periphery of the optical lens, and the optical lens is retained at the positions where the ribs are formed (i.e., by means of the projections). Thereby, tilt or eccentricity of the optical lens, which would otherwise be caused by “rattling” of a lens fit section, is prevented, and the lens optical axis can be aligned with high accuracy (see JP-A-11-84197 (FIG. 3), JP-UM-B-63-8884 (FIGS. 2, 3, and 4), JP-A-10-197772 (FIG. 2) and JP-A-2002-90604 (FIGS. 1 and 3)).
A lens barrel 100 according to the related art will be described by reference to FIG. 4.
FIG. 4A is a plan view showing that an optical lens 1 is attached to the lens barrel 100 of the related art. FIG. 4B is a cross-sectional view taken along line A-A shown in FIG. 4A. FIG. 4C is a perspective view of the lens barrel of the related art.
For attachment of the optical lens 1 to the lens barrel 100, the diameter of the optical lens is designed so as to become slightly smaller, as shown in FIG. 4A, in order to facilitate fitting of the optical lens 1. In short, rattling may occur in a lens fit section.
However, three ribs (projections) 101a to 101c are formed at uniform intervals on the inner periphery of the lens barrel 100 (a lens-retaining surface), whereby the optical lens 1 fitted into the lens barrel is brought into contact with and retained by the ribs 101a to 101c. Thus, tilt or eccentricity of the optical lens, which would otherwise be induced as a result of rattling having arisen in the lens fit section, can be prevented.
As shown in FIGS. 4B and 4C, according to the related art, three long-axis ribs (rod-shaped ribs) extending in parallel with the lens optical axis are formed on the inner periphery of the lens barrel 100. By means of long-axis ribs (projections) 101a to 101c formed so as to extend from the first lens-retaining surface to the second lens-retaining surface, a plurality of optical lenses (the first optical lens 1 and the second optical lens 2) are retained, thereby preventing tilt or eccentricity of the respective optical lenses and aligning the lens optical axis.
However, when a plurality of optical lenses are attached to the lens barrel of related art, the lens barrel 100 is resiliently deformed at the time of press-fitting of the first optical lens 1. Therefore, the force for retaining the second optical lens 2 originating from the long-axis ribs 101a to 101c formed on the inner periphery of the lens barrel is reduced, resulting in a failure to align the lens optical axis of the second optical lens 2 with high accuracy.
Namely, in the related-art lens barrel 100 having the long-axis ribs 101a to 101c formed on the inner periphery of the lens barrel, since the lens barrel 100 is resiliently deformed as the rib-formed positions expand during press-fitting of the first optical lens 1, the lens optical axis of the second optical lens attached to the lens barrel after resilient deformation cannot be aligned with high accuracy.